UK Simple wiring 101?

[MASHK71]

Hi Folks

I'm a DIY'er based in Hong Kong (same electrical system as the UK), and don't take on new electrical installations naturally, but do try to fix some simple problems.

The quick question:
2 spotlights to be connected into 2 terminal blocks buried (4 wires in total with 2 terminals blocks, protruding from some 35mm holes in the concrete) inside a wall, the 2 terminal blocks are dedicated terminals for spotlights connected in the past and removed because they (the spots) broke. Each Terminal block has 2 wires (the 4 wires in total described above) from the mains in their own terminals (1 x L & 1 x N) from one hole and (1 x N & 1 x E) from the other hole.

When testing with a basic voltage testing pen, there is current running to both terminal block when switched on at the wall. ( I haven't yet separated the wires from the terminal blocks and tested them individually, do I need to do that?)

But when connecting one of the lights (L to L and N to N naturally) it doesn't light up. Even if it did, I wouldn't know what to connect with the 2nd terminal block which has an N and an E wire.

What do I need to do to connect the lights correctly? It seems very unlikely, that the original sparky would have used a Green/Yellow wire for the live on one of the terminals, far more likely is that I'm missing a simple trick (running a blue between the 2 N's on the seperate terminal blocks to make this work?)

The new spots are 3W LED's each with their own little transformer connected, and naturally they both have 2 wires to connect them to the mains, a Brown (L) and a Blue (N)

The location is in a tiled concrete cavity above the bathroom mirror. I can't get access to the 2 sets of 2 wires protruding from the 35mm holes once they disappear up inside those holes without some major demolition work but I know that they're the same circuit as the switch at the wall, powers current to both terminal blocks on and off again when it's switched.

FYI
It's my friends flat,. I said I'd help out do some stuff in return for a few favours he's done me.

Thanks in advance for your help in advising a novice!

 

[littlespark]

Photos please, if you can.

I’ll try to be polite, ( I’m sure others won’t be!) but voltage pen is likely not giving a true reading. A two prong voltage tester would be better, or a multimeter set to AC volts

it’s unusual to just have a neutral and earth…. What is the cable? Normal twin and earth?

there may even be another cable that’s dropped into the wall you don’t know about.

 

[Pete999]

Hi Folks

I'm a DIY'er based in Hong Kong (same electrical system as the UK), and don't take on new electrical installations naturally, but do try to fix some simple problems.

The quick question:
2 spotlights to be connected into 2 terminal blocks buried (4 wires in total with 2 terminals blocks, protruding from some 35mm holes in the concrete) inside a wall, the 2 terminal blocks are dedicated terminals for spotlights connected in the past and removed because they (the spots) broke. Each Terminal block has 2 wires (the 4 wires in total described above) from the mains in their own terminals (1 x L & 1 x N) from one hole and (1 x N & 1 x E) from the other hole.

When testing with a basic voltage testing pen, there is current running to both terminal block when switched on at the wall. ( I haven't yet separated the wires from the terminal blocks and tested them individually, do I need to do that?)

But when connecting one of the lights (L to L and N to N naturally) it doesn't light up. Even if it did, I wouldn't know what to connect with the 2nd terminal block which has an N and an E wire.

What do I need to do to connect the lights correctly? It seems very unlikely, that the original sparky would have used a Green/Yellow wire for the live on one of the terminals, far more likely is that I'm missing a simple trick (running a blue between the 2 N's on the seperate terminal blocks to make this work?)

The new spots are 3W LED's each with their own little transformer connected, and naturally they both have 2 wires to connect them to the mains, a Brown (L) and a Blue (N)

The location is in a tiled concrete cavity above the bathroom mirror. I can't get access to the 2 sets of 2 wires protruding from the 35mm holes once they disappear up inside those holes without some major demolition work but I know that they're the same circuit as the switch at the wall, powers current to both terminal blocks on and off again when it's switched.

FYI
It's my friends flat,. I said I'd help out do some stuff in return for a few favours he's done me.

Thanks in advance for your help in advising a novice!

Note you cannot test fot current flow with a volt stick, only a dubious voltage will be senses these testers are an Electricians worst enemy ,totally unreliable, prone to picking up static voltages etc.

 

[MASHK71]

Photos please, if you can.

I’ll try to be polite, ( I’m sure others won’t be!) but voltage pen is likely not giving a true reading. A two prong voltage tester would be better, or a multimeter set to AC volts

it’s unusual to just have a neutral and earth…. What is the cable? Normal twin and earth?

there may even be another cable that’s dropped into the wall you don’t know about.

Thanks for the reply, Images attached (I knew I should have taken a shot of the installation)

As for the wire type, there is only insulation on each, (1.5mm) (including the 'earth' G/Y), there's no cable jacket (normal in HK) so I can't see how the wires are grouped together inside the wall.

Noted re the voltage pen, I will say that it gives a very definitive signal when the wall switch is on and zero signal when it's off.

If I used a two prong voltage tester (or M.meter), what would I be looking for exactly?

 

[MASHK71]

View attachment 87091View attachment 87092View attachment 87093


Thanks for the reply, Images attached (I knew I should have taken a shot of the installation)

As for the wire type, there is only insulation on each, (1.5mm) (including the 'earth' G/Y), there's no cable jacket (normal in HK) so I can't see how the wires are grouped together inside the wall.

Noted re the voltage pen, I will say that it gives a very definitive signal when the wall switch is on and zero signal when it's off.

If I used a two prong voltage tester (or M.meter), what would I be looking for exactly?

It seems I did take 1 photo after all, it doesn't really tell us much more other than the wires run inside tiled plywood.

The other hole (not pictured) is the same set up, except that the L is replaced by a G/Y insulated wire.

Does anyone have any more insight to add?

Thanks

 

[littlespark]

I think we need someone fluent in hong kong standards before further advise.

That cable looks big just for lighting.... and lack of sheath, or conduit is unusual.

I still think there's cables missing. minimum, you would need a live, neutral and earth at each hole.
You might need an inspection camera to look inside.

Is there no access to this void at all? screwed hatch, plasterboard on other side of wall that you could make a hatch?

 

[MASHK71]

I think we need someone fluent in hong kong standards before further advise.

That cable looks big just for lighting.... and lack of sheath, or conduit is unusual.

I still think there's cables missing. minimum, you would need a live, neutral and earth at each hole.
You might need an inspection camera to look inside.

Is there no access to this void at all? screwed hatch, plasterboard on other side of wall that you could make a hatch?

Many thanks for the diagnosis.

Hmmm welcome to HK, the standards here are the standards of the UK from 25 years ago that have largely gone unupdated in that time.

Added to that you have almost zero rule enforcement and a constant desire to save time and money and an ‘it’s somebody else’s problem’ attitude.

So yeah, a bit Wild West.

In HK all residential buildings are concrete, no wall cavities (generally) and no insulation (ever). So inspection hatches largely don’t exist and the wall

 

[MASHK71]

I think we need someone fluent in hong kong standards before further advise.

That cable looks big just for lighting.... and lack of sheath, or conduit is unusual.

I still think there's cables missing. minimum, you would need a live, neutral and earth at each hole.
You might need an inspection camera to look inside.

Is there no access to this void at all? screwed hatch, plasterboard on other side of wall that you could make a hatch?

Many thanks for the diagnosis.

Hmmm welcome to HK, the standards here are the standards of the UK from 25 years ago that have largely gone unupdated in that time.

Added to that you have almost zero rule enforcement and a constant desire to save time and money and an ‘it’s somebody else’s problem’ attitude. So yeah, a bit Wild West.

In HK ‘all’ residential buildings are tower blocks and built of concrete, no wall cavities and no thermal insulation (ever). Internal Dividing walls are either steel reenforced concrete, concrete, or rendered breeze block / brick (i repeat there are no cavities) hence inspection hatches largely don’t exist and the wall that this plywood channel is built against is concrete.

Plasterboard is used sometimes, but only really to cover block walls rather than render and plaster. Consequently the risk of fire is lower (but the consequences higher - tower blocks) and I seldom see sheathing on cables, just insulated 1.5 or 2.5mm individual wires inside conduit inside a concrete wall, that’s it......Or sheathing inside concrete (not both)

See attached image from my flat. When some remodelling was done, the wiring for the lights was extended and new wiring added for another AC unit. Sheathing without conduit or conduit without sheathing...... and no earth for the lights.

Conduit would have been used inside all the concrete walls, in this the bathroom lights building (as it is in all of them) but when someone remodelled their basic bathroom, the contractor, seeking to cut as many corners as possible would have just built a plywood box around the wires to act as a housing for the lights. In his mind, if it looks ok, that’s all that matters - the plywood box is the conduit for the wires - welcome to China.

This is another room in a different building that wants some work doing and is absolutely typical. Wires in conduit until they exit the wall, and then....anything goes. Wires ‘terminated’ with a scrap of insulation tape and left in a tangled heap....

So back to the job at hand..... I guess I can fish around inside the void with some hook and see if I can pull out any more wires...., but even then, even if I find any, there is nowhere to attach any earth to the light housing - I could improvise that. The lights have L and N only....

Is there anything else I can do, a photo inside the switch for these lights that will help me get an answer from afar?

Many thanks